1. Field of the Invention
The present invention relates to a roller bearing with a cage on which a large load or an impact load is to be imposed, and more specifically, to a technology to facilitate the assembly or to enhance the durability thereof.
2. Related Background Art
A roller bearing with a cage is frequently used for supporting a gear shaft, a spindle, rollers, etc., since in a reduction apparatus for a rolling mill, a pinion stand, a crusher, or the like, a large load or an impact load is caused to act on each of the constituent parts and, moreover, the apparatus itself vibrates severely. With such roller bearing with a cage, rollers are supported by a pin-type cage or a stud-type cage so that a friction or damage of rollers and the main body of the case caused by the mutual contact is not brought about, and the rollers can be securely retained.
A roller bearing with a pin-type cage is a bearing for retaining rollers by means of a pin-type cage which comprises a plurality of pins and a pair of annular side plates for supporting the rollers to be rotatable. Such roller bearing is described in Japanese Utility Model Publication No. 49-37730, et al., and a structure in which such pin-type cage is applied to a conical roller bearing is shown in FIGS. 10 and 11.
In a pin-type cage 13 of a bearing 1 shown in FIG. 10, pins 11 and an annular side plate 17 are connected with each other by use of parallel screws, while the pins 11 and an annular side plate 15 are connected with each other by means of welding. More specifically, parallel screw portions 71 are formed at the fore ends of the pins 11, and after these parallel screw portions 71 are inserted into through holes 73 which are formed on the annular side plate 17, nuts 75 are screwed onto the parallel screw portions 71, whereby the pins 11 and the annular side plate 17 are connected with each other. On the other hand, flange portions 77 are formed at the hind ends of the pins 11. After these flange portions 77 are fitted in recesses 79 formed on the outer side surface of the annular side plate 15, a weld is carried out to connect the pins 11 with the annular side plate 15. It should be noted that when the pin-type cage 13 is to be assembled, the pins 11 and the annular side plate 17 are connected with each other after the pins 11 are inserted through rollers 7.
Also, in a pin-type cage 13 of a bearing 1 shown in FIG. 11, a pin 11 and an annular side plate 15 are connected with each other by means of welding. On the other hand, the pin 11 and an annular side plate 17 are connected with each other by means of a cone screw. More specifically, a cone screw portion 81 is formed at the fore end of the pin 11, and this cone screw portion 81 is screwed into a cone screw hole 83 which is formed on the annular side plate 17, whereby the pin 11 and the annular side plate 17 are connected with each other.
On the other hand, a roller bearing with a stud-type cage is a bearing for retaining rollers by means of a cage which comprises a plurality of stud pins and stay-type pins and a pair of annular side plates. This roller bearing is described in U.S. Pat. No. 4099803, et al., and a structure in which such stud-type cage is applied to a cylindrical roller bearing is shown in FIG. 12.
In a stud-type cage of a bearing 1 shown in FIG. 12, a stay 55 and two annular side plates 15 and 17 are connected with each other by press fitting or welding, meanwhile cylindrical rollers 7 are retained to be rotatable by stud pins 85 which are press fitted in the inner surface sides of the both annular side plates 15 and 17.
There exist various demands for the above-mentioned roller bearing with a cage, in order to enhance the assembling performance or improve the strength of the bearing, or the like.
For example, in the pin-type cage shown in FIG. 10, which uses the parallel screws for connecting the pins 11 and the annular side plate 17, a jig is required for adjusting a space between the both annular side plates 15 and 17, and moreover, close attention much to be paid when each nut 75 is fastened, which results in a very poor assembling performance. On the other hand, with respect to the pin-type cage shown in FIG. 11 which uses the cone screws, if a manufacturing error of a referential diameter of the cone screw is great, the axial position of the pin 11 with respect to the annular side plate 17 becomes hardly constant, so that the cone screw portion 81 may extrude inside the annular side plate 17, as shown in FIG. 13. In this case, a stress is concentrated on a trough of the cone screw portion 81 so that the strength of the pin 11 is decreased and the pin 11 may be broken or damaged due to its long use under severe use conditions. In addition, also in the roller bearing with the stud-type cage shown in FIG. 12 in which a pin-type stay 55 is press fitted into the two annular side plates 15 and 17 and welded together, a jig is required for adjusting a space between the both annular side plates 15 and 17. Moreover, if a space between the both annular side plates 15 and 17 is too narrow, the adjustment thereof is difficult, which results in a problem of a very poor production yield.
The pin 11 (or the stay-type pin 55) and the annular side plate 17 (or the annular side plates 15 and 17) are connected together by means of welding, as shown in FIG. 14 (showing the essential part of the roller bearing with the pin-type cage of FIG. 11). However, it is difficult to evaluate the quality of the welding part itself at a low cost, and there is another problem that some limitation may be placed on the hardening treatment or the like of the pin 11. That is, though it is desirable that the pin 11 and the stay-type pin 55 be subjected to carburization or quenching treatment to enhance the hardness thereof, it is difficult to conduct such treatment on the entire body of the pin 11 or the stay-type pin 55 in order to prevent cracks in welding. As a result, it is difficult to reduce a frictional abrasion caused by the contact with a roller 13 or enhance the strength of the pin 11 or the stay-type pin 55 itself in a part in which a range for conducting the hardening treatment is restricted so that a desired hardness can not be obtained.
On the other hand, about a half of a load which is applied onto the pin 11 from the roller 13 is caused to act on a contact portion with the annular side plate 15. However, in the above-mentioned conventional roller bearing, the flange portion 77 is positioned outside of the annular side plate 15 so that the length of action becomes large. As a result, a stress generated in the welding portion becomes great, which is disadvantageous for the purpose of enhancing this strength of the portion.